One of the common types of fishing sinkers is made of lead, as lead is both inexpensive and easily configurable for attachment to a fishing line. From time to time, concerns about toxicity caused by lead in the environment has led to a search for substitute materials to be utilized in fishing sinkers. However, other materials lack the high specific gravity of lead and are therefore less desirable, consequently, lead continues to be used in fishing sinkers. One of a potential of alternate metals having a high specific gravity is bismuth. Unfortunately, bismuth is a fragile metal that renders it unsuitable for use in fishing sinkers in most cases due to the difficulty of extracting a bismuth sinker from a mold cavity. Bismuth has been alloyed with various metals such as tin for use in waterfowl shot. For example, the Griffin U.S. Pat. No. 5,719,352 suggest one should alloy bismuth with tin or lead and the article by Brown points out that the use of bismuth tin alloys in shot for waterfowl hunting has been increasing since 1994 with the waterfowl shot comprising a bismuth alloy of 97% bismuth and 3% tin. Alloys suitable for waterfowl shot are not necessarily suitable for fishing sinkers, since use of a bismuth alloy in shot is a one time event and the use of a sinkers involves subjecting the sinker to repeated abuse with the sinker retaining its integrity over a period of use.
In addition to the problem of fragility of bismuth, bismuth alloys, which might be lighter and potential less fragile, are difficult and time consuming to cast since certain bismuth alloys expand as they solidify. The expansion causes the solidified object to adhere to the mold, which males it a difficult and time consuming to extract the solidified object from the mold. If one is making multiple items, such as inexpensive fishing sinkers, it becomes prohibitively expensive to individually extract each sinker from the mold. The present invention provides a bismuth alloy sinker of sufficient integrity as well as a method of casting multiple bismuth alloy sinkers that allows one to quickly and easily remove the solidified sinkers from the mold.
Thus, in one embodiment the present invention provides an environmental friendly sinker by alloying bismuth with another metal to takes advantage of the high specific gravity of bismuth while the alloying of the metal with bismuth produces a sinker of sufficient strength and integrity so as not to break and of sufficiently high specific gravity so that the sinker will sink itself as well as fishing tackle connected thereto.